NAN agents are extremely toxic and require adequate protection. It is recommended to wear category III filtering PPE, butyl gloves and overboots, and a protective mask with an appropriate filter cartridge.
NAN: What are they?
The first organophosphate neurotoxic agents were developed in the 1930s following Schrader’s work for the German army, including tabun, sarin, and soman. These were designated as type G agents (G for German). In the 1950s, type V agents (V for Venomous) were initially synthesized by British chemists, followed by similar products developed by various countries (VX, VR, CVX, etc.). In the 1970s, as part of a secret program, type A agents were developed by the Soviets (A-230, A-232, etc.), some of which are known as Novichoks. Starting in the 1990s, following the collapse of the Soviet bloc, data from this program began to enter the public domain. In 2018, the identification of the A-234 agent used in the attempted poisoning of Sergei Skripal, a former Russian agent, led to OPCW investigations, resulting in some states proposing the inclusion of “new neurotoxic agents” in Schedule 1 of the agents covered by the Chemical Weapons Convention. This includes a specific compound and two families of organophosphates, as well as a family of carbamates whose potential use as chemical warfare agents had already been discussed.
Note: Some type A agents have not (yet) been included in Schedule 1 (e.g., A-262 or one of its analogs, likely used in the poisoning of Alexei Navalny in August 2020).
NAN Characteristics
NAN encompasses hundreds of distinct products.
Public data on NAN is still scarce. Studies are ongoing in various countries to better characterize them.
Some type A organophosphate compounds are described as having potentially equal or greater toxicity than VX.
These agents are considered relatively persistent, low-volatility, and stable. They are thus contaminating and can be easily transferred from a contaminated surface to a clean one. Similar to VX, they are likely absorbed quickly through the skin, where they can accumulate and be slowly absorbed into the bloodstream. Therefore, treatments for intoxication may be lengthy (several days or even weeks) before complete neutralization and elimination.
Agents A-230, A-232, A-234 are liquids at room temperature (15-20°C), while agents A-242 and A-262 are solids.
They are relatively soluble and stable in water, solvents, and oil.
What Personal Protective Equipment for NAN?
According to American recommendations (January 2019 guide on new organophosphate neurotoxic agents), PPE requirements are similar to those recommended for VX exposure (persistent agent, very low volatility, stable, relatively water-soluble).
The exposure risk is mainly through contact with a contaminated surface, ingestion of a contaminated liquid or solid (e.g., a powder like fuller’s earth), or inhalation of an aerosol (liquid or solid).
What protective clothing?
High protection factors obtained during VX agent tests validate the protection of clothing against NAN due to the similar chemical properties of these agents. The NAN guide, “Guide to Best Practices in the Presence of NAN,” SGDSN, 06-12-2021, evaluates among other things the POLYCOMBI®. The POLYCOMBI® suit is less permeable to NAN than some non-filtering type 3 suits. It protects the wearer for at least 4 hours after contamination, as indicated in the table below from the SGDSN guide:
These initial test results on NAN validate the performance of the activated carbon microbead technology used in certain PPE ranges.
What protection for extremities?
Given the contamination transfer characteristics from one surface to another, protecting extremities is crucial in body protection. The SGDSN guide recommends hand protection with butyl gloves. Thus, a protection system with butyl gloves and overboots, showing good results in VX tests (24-hour protection according to NATO standards), is a viable solution for body protection against NAN.
OUVRY has developed corresponding equipment such as CBRN OBOOTS® overboots and OG05® gloves. VX tests show no permeation with this type of protection.
What protection for respiratory tract and face?
Respiratory protection involves using an CBRN gas mask with the appropriate protection cartridge. The interface between the mask and the suit is a preferential penetration zone for NAN.
The CBRN gas mask must be adaptable to a wide range of protective suits. Specific developments by OUVRY validate this protection at the interface between the OC50® mask and various suits, including the POLYCOMBI®.
An appropriate respiratory protection cartridge must be used with the mask (e.g., CFO CBR®).
Bibliography
- Opravil et al. (2023) Arch Toxicol, 97 : 2587-2607. A-agents, misleading known as « Novichoks » : a narrative review
- Pampalakis & Kostoudi (2023) Int J Mol Sci, 24, 8600. Chemical , physical, and toxiclogical properties of V-agents
- Fouth generation agents, reference guide (Information of January 18, 2019), USA
- OPCW, S/1621/2018, 2 May 2018. Note by the Director-General : request for information from states parties on new types of nerve agents